If you’ve gone to the Google home page today you’ll notice a new doodle—one celebrating the company’s 18th birthday. However, as Wired points out, Google’s birthday has shifted over the years. The company was officially incorporated on September 4, 1998 (but the research that led to Google began two years earlier), yet the company has never celebrated that date. In 2004 Google celebrated its birthday on September 7. In 2005 it celebrated its birthday on September 26. One year it celebrated its birthday on September 8. But hey, now that the doodle is out, Google says September 27 is its birthday—at least for this year.